1. Field of the Invention
The present invention relates to an apparatus for lifting, excavating, splitting and/or crushing tree stumps, or other materials, such as wooden or metal materials that may be present at an excavation site. The apparatus is characterized in part by a two pivot point design.
2. Background
A number of mechanical devices have been developed for the crushing and demolition of a variety of materials, including wood. Certain of these devices utilize a frame having an upper and lower jaw for gripping and cutting the material or work product.
For example, U.S. Pat. No. 5,533,682 describes a device for crushing and/or cutting concrete, cutting iron sections and/or scrap iron, and cutting and splitting wood. The device comprises a frame having a first jaw that is stationary with respect to the frame, and a second jaw that is pivotable by means of a setting cylinder. While the fixed first jaw is intended to support the material being cut, the pivotable jaw includes a pointed crusher tooth and knife-like section that facilitate the cutting of the material.
This device offered some advantages over the art. For example, the jaws of the device were detachably connected to the frame, so that a different set of jaws could be used for different materials being cut. Thus, one device could be used for multiple purposes, as long as one purchased the appropriate sets of jaws.
However, this type of device presented certain limitations as a wood splitter and crusher. The particular embodiment described as being suited for cutting and splitting wood employed two serrated strips located on the inner surface of the fixed jaw to prevent slippage of the wood during the cutting process. While this design may be effective for cutting smaller sections of wood, logs, root ends and the like, when cutting larger sections of wood, e.g., tree stumps, forward slippage of the wood becomes highly problematic. Further, the force of the pivotable jaw upon the stationary jaw could lead to dislodgement or misalignment of one or more of the jaws with respect to the frame.
A similar device intended for use in the demolition of iron or steel reinforced concrete structures is disclosed in U.S. Pat. No. 5,146,683. This device, termed a reinforcement cutter, also employs a moveable upper jaw and a stationary lower jaw configuration. The device further includes a first and second shearing cutter means that are dismountably secured to each of the opposed inner lateral surfaces of the upper and lower jaws in a bent formation. As in the case above, however, the potential for forward slippage of the wood and/or dislodgement of one or more of the jaws is problematic when using this device for cutting and splitting large sections of wood.
Other devices for splitting and crushing tree stumps have been developed that utilize a bit/counter bit configuration.
Swedish patent publication 378,502 describes a splitting bit that is pressed between two counter bits. The counter bits are disposed at the adjacent upper edges of arm-like structures that support the tree stump, and have an arcuate shape that facilitates the holding of the stump.
However, this configuration has several disadvantages. For example, the area or slit between the counter bits tends to get clogged with debris from the splitting and crushing procedure, particularly at the base section of the slit. This clogging requires that the apparatus be shut down and the slit cleared from time to time during the splitting and crushing procedure. It is also possible that rocks coming up with stump roots may penetrate or lodge in the slit between the counter bits thereby causing damage to the counter bits. Additionally, the arcuate design of the bits can be problematic when replacing dulled bits. Further, unless the pivotable bit is manufactured such that it aligns precisely with the slit between the counter bits, damage to the apparatus is very possible.
U.S. Pat. No. 5,080,151 to Pallari describes a tree stump lifting and crushing apparatus comprising one or more lifting hooks and a bit which is pivotable and turnable against a counter bit for crushing tree stumps placed therebetween. The pivotably closable bit and counter bit include a cutting surface and a counter surface. The counter surface is substantially continuous and extends across the width of the cutting surface upon closing of the bits. A closure stop means is provided that is intended to prevent destructive engagement of the cutter surface and counter surface.
Though somewhat of an improvement over the prior art, serious problems were encountered by this apparatus. For example, effectively securing the tree stump during the lifting and crushing procedure remained problematic. Additionally, the area or slit existing between the stump hooks invited the same debris and clogging as the devices of the prior art. Consequently, similar limitations were observed in terms of downtime and potential for damage to the apparatus.
There remains a need for an apparatus to securely lift, excavate, split and crush tree stumps that avoids the various problems of the prior art. Specifically, it would be highly desirable to develop a tree stump lifting and crushing apparatus that would offer an increased holding area for the grabbing and subsequent handling of the tree stump during the cutting process. It also would be highly desirable to develop a tree stump lifting and crushing device that could securely hold the tree stump during the cutting process such that forward slippage of the stump would be prevented. It also would be highly desirable to develop a tree stump lifting and crushing device that would avoid the inherent limitations associated with the devices of the prior art that have a stationary jaw configuration. Further, it would be highly desirable to develop a tree stump lifting and crushing device that would avoid the debris and clogging problems seen in the devices of the prior art.